1. Field of the Invention
The present invention relates to a driving system for auxiliaries or auxiliary machine of an engine and a method for adjusting tension of a belt for driving the auxiliaries and, more particularly, to a driving system for auxiliaries for an engine, so adapted to be driven by a belt and to a method for adjusting the tension of the belt for driving the auxiliaries.
2. Description of Related Art
Auxiliaries or auxiliary machine disposed to the engine body may include, for example, an alternator, a pump for an air conditioner, a pump for cooling water, i.e. water pump. These auxiliaries are mechinically connected to an output shaft of the engine so as to be driven directly by output of the engine.
As technology involved with a driving system for auxiliaries, Japanese Utility Model Laid-open (kokai) Publication No. 80,127/1986 discloses an example in which a crank shaft functioning as the output shaft of the engine is connected through a belt to various auxiliaries.
U.S. Pat. No. 4,502,345 discloses a system in which a pump for an air conditioner is connected to a crank shaft through a belt as well as a cam shaft is also connected to a water pump, etc., through the belt. It can be noted herein that the cam shaft is such that generally it is connected to the crank shaft through a timing belt, so that it can be classed with the crank shaft as a source of driving the auxiliaries.
Heretofore, a driving system for auxiliary has been commonly constructed in such a manner that a plurality of auxiliaries are driven by a common belt. For instance, Japanese Utility Model Laid-open (kokai) Publication No. 80,127/1986 discloses the driving system for auxiliaries constructed such that the alternator and the water pump are to be driven by a first common belt and that the pump for power steering and the pump for air conditioner are to be driven by a second common belt.
Further, U.S. Pat. No. 4,502,345 discloses the driving system for auxiliaries, in which the pump for air conditioner is to be driven by a first belt wound around the crank shaft and the cam shaft and the pump for the power steering is to be driven by a second belt wound around the crank shaft and the cam shaft, while the water pump and the alternator are to be driven by a common belt wound around the cam shaft.
It should be noted, however, that the driving of two auxiliaries by one belt presents the following problems. More specifically, when two auxiliaries are driven by the belt wound around the crank shaft and the cam shaft, as shown in U.S. Pat. No. 4,502,345, the crank shaft serves as a driving axle while the cam shaft serves as a following axle, so that the crank shaft cannot be classed with the cam shaft.
Hence, when a conventional layout for the driving system for the auxiliaries is adopted, the following problems may occur:
1. Vibration is likely to occur with respect to the belt; and
2. It is difficult to ensure reliability upon operation of auxiliaries.
In order to ensure reliability upon operation of the auxiliaries, therefore, it is desired to drive each of the auxiliaries by respective and separate belts. It is further desired in this case that a tensioner is to be mounted to each of the belts so as to adjust the belts as well as to suppress the tension thereof, in order to compete with elongation of the belts.
It can be noted, however, that the disposition of the belts and the tensioners for the respective auxiliaries necessarily leads to an increase in the number of parts, thereby making the structure of the engine more complex and larger. It is thus necessary to simplify the structure of the engine and decrease the number of parts when each of the auxiliaries is to be driven by the separate belt.